This invention relates to an improvement in a vertical kiln apparatus. In this apparatus an aggregate material, after being fired in the kiln chamber, flows downwardly onto a shelf below the chamber. The aggregate is continuously displaced from the shelf, in volumetrically equal increments, to induce uniform gravity flow of the aggregate through the kiln.
Vertical kilns are used for various applications, such as firing of limestone aggregate to produce lime. A typical commercially available vertical kiln is a structure having a vertical cylindrical shaft which provides a kiln chamber. Pipes which include flame nozzles are positioned crosswise in the kiln chamber to provide a firing zone. These pipe structures are usually referred to as firing beams.
In the kiln structure described above the firing beams cause a problem which is difficult to overcome. For example, in the manufacture of lime in a vertical kiln the limestone aggregate (crushed limestone) is introduced through the top of the kiln chamber. As the stone falls downwardly in the kiln chamber it passes first through a preheat zone, then through a firing zone, and into a cooling zone at the bottom of the kiln. The firing zone is the middle part of the kiln chamber in which the crosswise firing beams are positioned. The presence of the firing beams disrupts the normal flow of the aggregate, thus causing the aggregate to move at an erratic rate through the firing zone. The result of this erratic flow rate is a variance in the residence time of the aggregate in the firing zone, so that inevitably some of the stone is overburned and some is underburned. It follows, therefore, that to produce a uniformly, high quality aggregate in a shaft kiln, it is essential that the aggregate flow at a controlled, uniform rate through the firing zone.